1. Field of the Invention
The present invention relates to a pump unit.
2. Related Art
In a pump unit which is configured such that rotational power from a driving source can be transmitted to an actuator via a pair of operating oil lines, it has been conventionally known that, in addition to a first hydraulic pump main body operatively connected to the driving source, there are provided a second hydraulic pump main body and a PTO clutch mechanism.
For example, Japanese Patent Application Laid-open No. 2003-291,674 has proposed a pump unit comprising: a first pump shaft operatively connected to a driving source; a first hydraulic pump main body rotatably driven by the first pump shaft; a second pump shaft operatively connected to the first pump shaft; a second hydraulic pump main body rotatably driven by the second pump shaft; a PTO shaft operatively connected to the first pump shaft; a PTO clutch mechanism interposed on a transmission path from the first pump shaft to the PTO shaft; and a pump case, which supports the first pump shaft, the second pump shaft and the PTO shaft, and further, accommodates therein the first hydraulic pump main body, the second hydraulic pump main body and the PTO clutch mechanism.
The above-described pump unit in the prior art has been configured such that a first transmission gear supported by the first pump shaft in a relatively non-rotatable manner, a second transmission gear supported by the second pump shaft in a relatively non-rotatable manner in a state operatively connected to the first transmission gear, and a PTO transmission gear non-rotatable relatively to a driving-side member of the PTO clutch mechanism in a state operatively connected to the first transmission gear are adapted to transmit power from the first pump shaft to the second pump shaft and the PTO clutch mechanism. Here, the compactness of the entire unit has been susceptible to improvement.
Specifically, in the case where the first and second hydraulic pump main bodies are of a variable displacement type, the first and second hydraulic pump main bodies are provided with movable swash plates, respectively, besides cylinder blocks rotatably driven by the corresponding pump shafts and piston units accommodated in a non-rotatable but axially slidable manner relatively to the cylinder blocks.
The movable swash plate can be oscillated on an operational axis perpendicular to the corresponding pump shaft by an outside operation in a state inserted around the corresponding pump shaft, such that a suction/discharge oil quantity of the cylinder block can be varied by changing a slide range of the corresponding piston unit according to an oscillation position of the swash plate.
In other words, in the case where the above-described hydraulic pump main body is of the variable displacement type, both of the movable swash plate and the transmission gear must be disposed on the corresponding pump shaft. In the configuration, the oscillation range of the movable swash plate has been secured by separating the transmission gear from the corresponding movable swash plate along the axial direction of the pump shaft in the above-described pump unit in the prior art. Therefore, the pump unit cannot be satisfactorily reduced in size in the axial direction of the pump shaft.
The present invention has been accomplished to solve the problems experienced by the above-described prior art. Therefore, it is a principal object of the present invention to provide a pump unit which can be reduced in size as much as possible in the pump unit, in which a movable swash plate and a transmission gear are disposed on a pump shaft.